1. Field of the Invention
This invention relates to a high speed boat having a bottom engine exhaust.
2. Description of the Prior Art
In the past, boats have discharged the engine exhaust gas into the atmosphere, and were required to install muffler devices, resulting in the disadvantages that the power output was reduced and the boat's weight was increased. Therefore, it has been proposed in Japanese Pat. No. 932,781 to discharge the exhaust gas to the boat's bottom, as shown in FIG. 1 and FIG. 2. In the bottom exhaust system, the main exhaust pipe b of the boat's engine a opens into the water at the boat's bottom c near to the stern of the boat. Further, an auxiliary exhaust pipe d is branched from the main exhaust pipe b to open to the atmosphere for the discharge of exhaust during stopping, slow forward travel and when moving backwards.
A groove e is formed in the boat's bottom along the longitudinal direction of the boat and extends forward from the ship's stern. The front wall f at the deepest part of the groove e and the ship's body g define a stepped portion h. The main exhaust pipe b is opened to the bottom c of the groove e at a portion near to the step h.
When this prior art device was applied to a boat of the 40 ton displacement class, the static pressure at the exhaust port in the boat's bottom was lower than the atmospheric pressure when the ship was moving at a speed of 5 to 4 knot or more, causing an increase in the suction of the engine, a corresponding increase in efficiency of the engine and a reduction in the fuel consumption.